In clean rooms used in factories or research laboratories in the relevant field of semiconductors, in foodstuffs, in medicines, and in biotechnology, dry air filters for trapping air-born particles are disposed to air introduction paths, and air passing therethrough is introduced into the clean room.
Air filters currently used in clean rooms include ULPA (abbreviation for Ultra Low Penetration Air) with uses glass fibers for the filter medium and HEPA (abbreviation for High Efficiency Particle Air), Such filters are excellent for removing dusts, for example, ULPA filters can remove fine particles as small as 0.1 .mu.m. Further, non-glass type filters with fluoro resin or quartz fibers, instead of the glass fibers, for the filter medium have been developed so as not to release inorganic substances from the air filters.
Recently, with the increase of integration degree of semiconductors, diffusing gaseous organic substances as well as dusts from the clean room air has been considered to be the cause of defects. It has been pointed out that organic substances are adsorbed on the surface of semiconductor substrates (silicon wafers) in clean rooms, deteriorating device characteristics (Fujii, "Gaseous Contaminants and Current Situation for Countermeasure of Removal", Air Cleaning, Vol. 32, No. 3, p 43 (1994), published from the Foundation of Japan Air Cleaning Society).
Further, it has been well known that an n-type semiconductor is obtained by doping P (phosphorus), and a p-type semiconductor is obtained by doping B (boron) into a silicon wafer in semiconductor manufacturing steps However, if phosphorus compounds or boron compounds are present in the clean room air, these may cause unnecessary doping, so that it is necessary to remove such ingredients from the clean room air.
The present invention has been developed to solve the problems described above and it is an object thereof to provide an air filter for trapping air-born particles that can eliminate the presence of gaseous organic substances, for example: in clean rooms, semiconductor production apparatus` or the like, a method of manufacturing an air filter therefor, a treatment agent constituting the air filter, a method of manufacturing a filter medium, a clean room and a local facility, such as a semiconductor production apparatus, in which gaseous organic substances are not present; as well as in a clean room and a local facility in which phosphorus compounds and boron compounds are not present.